In portable, battery powered, devices it is vital to economize the energy resources. Therefore, minimizing the required amount of power is always a major concern when designing portable electronic apparatuses, such as mobile telephones and laptops. In these apparatuses, any integrated camera is often one of the larger energy consumers. This is especially true if the camera has a large image sensor and/or if it is used to capture moving images, i.e. video data. Further, there is a trend to include eye-tracking based solutions in portable devices. An eye/gaze tracking system is associated with especially demanding energy requirements because, here, high-resolution video capturing must normally be combined with data processing tasks of relatively high intensity.
To reduce the energy consumption in portable devices various solutions are known. For instance, US 2010/0079508 describes an electronic device with gaze detection capabilities, wherein a power management scheme is applied, which is based on whether or not a user's gaze is detected. In the absence of a user looking at the device, e.g. the display screen may be turned off.
US 2008/0111833 describes another eye-tracking related solution. Here, the display brightness is adjusted based on where the user's gaze is estimated to be located. Thus, a screen region around the gaze point is made relatively bright while remaining areas of the screen are darker.
U.S. Pat. No. 7,379,560 discloses a solution for monitoring human attention in dynamic power management. Here, an image-capturing device is used to analyze a user's face and learn his/her behavior. When the system determines that the user does not pay attention to the display, the power consumption of one or more components in the system is reduced.
U.S. Pat. No. 6,526,159 reveals a solution, wherein resources and power are managed based on eye tracking. Specifically, an orientation of an eye is determined, and on the basis thereof, the operating system changes the resources allocated to a display device.
Moreover, it is generally known that a camera can be set in an active mode or a standby mode, where the latter is associated with very low energy consumption. When set in the standby mode, the start-up delay until the camera may start capturing image data is very short compared to if the camera had been shut off completely. Consequently, the standby mode is useful when the camera is needed intermittently with short notice during limited periods. In continuous operation, however, the active mode is the only option.
Thus, there exist means, e.g. eye-tracking based, to reduce the power consumption in general mobile devices as well as in cameras. Nevertheless, there is yet no efficient solution for lowering the energy requirements of an eye tracking system as such in steady-state operation.